Lenses can be made of many different types of transparent materials, such as glass or plastic, for example. Plastic lenses have increased in popularity in part because of relatively low cost and light weight. However, plastic lenses are generally more susceptible to abrasion and scratching. Glasses, including sunglasses, having plastic lenses also have wide popularity. However, most lenses do not filter out ultraviolet light, which is known to be harmful to eyes. For example, exposuee to ultraviolet light can cause brown cataracts.
Sunglasses that do not filter out ultraviolet light can be even more dangerous, primarily for two reasons. First, the user is more likely to look at the sun more frequently, thereby increasing exposure to harmful ultraviolet rays. Second, dark lenses cause the pupils to expand, thereby allowing more ultraviolet light to enter the eye.
A need exists for a lens and in particular, an optical lens that has good abrasion and scratch resistance. A need also exists for such a lens that acts as a filter for light in the ultraviolet spectrum and other damaging wavelengths to protect eyes from such radiation that can cause brown cataracts. It is known that ultraviolet radiation (ultraviolet light has a wavelength range of from about 10 nanometers to about 390 nanometers) and violet light in the range of from about 390 to about 450 nanometers can be damaging to the human eye. It is known that light at a wavelength of 425 nanometers is the most dangerous from the standpoint of brown cataract formation. A need also exists for such a lens that is not dark colored, to enable use in regular eyeglasses or ophthalmic applications, for example.
Various attempts to coat optical lenses have been made.
European Application No. 101326, filed 2/22/84, discloses a plastic lens having an abrasion resistant coating thereover. The coating is formed by applying a liquid organosilanol material of a specific type and thereafter curing the coating by a glow discharge treatment.
U.S. Pat. No. 4,474,857 discloses a clear coated article with a silicone resin coating containing colloidal silica and a uv absorber. According to the disclosure, the coating is formed from an aqueous coating composition that comprises a dispersion of colloidal silica in an aliphatic alcohol-water solution of the partial condensate of a silanol compound of a specific formula.